The decline in YPF follows plans by the Argentine government to acquire 51% of YPF. Already, the government has appointed two ministers to oversee the company, giving them all of the powers of the board of directors.

If Argentina pursues its takeover bid, Repsol said it would fight to obtain what it called a fair price for its majority stake in YPF.

"Repsol will resort to international arbitration tribunals and seek to press individual charges, as well as class actions, anywhere and everywhere that can get us a result," said Kristian Rix, deputy director of international and financial media at Repsol.

The Argentine government still has not determined how much it would pay Repsol for its YPF stake.

Earlier, Repsol had valued its YPF stake at $10.5bn (€8bn), based on a formula that assumes a share price of $46.55.

Investment bank UBS said estimated that Repsol may seek $18bn or more for its stake.

YPF’s output accounted for about 34% of the nation’s production in 2011, according to Argentina energy secretariat data.

YPF is also the country’s largest fuel retailer and refiner, with 52% of refining capacity and one of the largest petrochemical producers.

YPF owns several industrial sites, including La Plata in Buenos Aires, Lujan de Cuyo in the state of Mendoza and Plaza Huincul in the state of Neuquen. YPF also owns half of the Refinor plant in the northern state of Salta, according to YPF.